UI Freeze when using RushCore.getInstance().deleteAll(Class, callback)

[zoharyosef]

This is similar to #111
After a lot of deleting and saving, (in my app this happens on every load)
when using .deleteAll(Class, callback), ui freezes (just before the callback is called),
log shows "VACCUM",
and the freeze time gets longer and longer.

Thanks again!
Zohar